operand1 = int(input("input a number:"))  #输入第一个数
operator = str(input("input a operater(+ - * /):")) #输入运算符号
operand2 = int(input("input a number:")) #输入第二个数
if operator == "+":
    print(operand1+operand2) #输出两数相加
elif operator == "-":
    print(operand1-operand2) #输出两数相减
elif operator == "*":
    print(operand1*operand2) #输出两数相乘
else:
    operator == "/"
    print(operand1/operand2) #输出两数相除